Method of extending pot life of coating compositions

ABSTRACT

A liquid coating composition is disclosed that is prepared from a reaction mixture comprising an amine component comprising (a) an amine component comprising a polyamine complexed with CO 2  and (b) a crosslinker, wherein the amine component is liquid at ambient conditions.

FIELD OF THE INVENTION

The present invention relates to a carbon dioxide amine complex for usein a coating composition, more a particularly for use in a coatingcomposition containing reactive amines.

BACKGROUND OF THE INVENTION

Crosslinked coating compositions that are based on an amine componenttypically are produced from two component systems that, when the twocomponents are mixed together rapidly, cure at ambient conditions. Thepot life of such coating compositions produced from amine functionalcomponents can be extended by converting the amine component to arelated salt complex. For example, when carbon dioxide (CO₂) is reactedwith amine, the amine forms a carbamate salt that is solid at roomtemperature. Upon heating, the CO₂ complexed with the carbamate salt isreleased and a liquid amine is then regenerated to function as a curingagent for the coating composition. Upon reaction of the amine with anisocyanate, polyurea may be formed. Other functional groups reactivewith an amine may be included to produce other coating compositions.

In this process, an amine that is liquid at ambient conditions can beadded to a solvent and gaseous CO₂ is bubbled through the solution inorder to react the CO₂ with primary amines and/or secondary amines andform a carbamate salt. It is believed that the carbamate formulationoccurs by forming a carbamic acid moiety in the presence of an amine(primary or secondary) whereby the carbamic acid protonates and forms asalt. Such salt complexes have been used to produce powder coatingapplications requiring an amine.

SUMMARY OF THE INVENTION

The present invention includes a liquid coating composition preparedfrom a reaction mixture comprising (a) an amine component comprising apolyamine complexed with CO₂ and (b) a crosslinker, wherein the aminecomponent is liquid at ambient conditions. Also included in the presentinvention is a method of producing a coating composition comprisingapplying onto a substrate a liquid reaction mixture comprising (a) anamine component comprising a polyamine complexed with CO₂ and (b) acrosslinker, wherein the amine component is liquid at ambientconditions, whereby the polyamine disassociates from the CO₂ and reactswith the crosslinker.

DESCRIPTION OF THE INVENTION

For purposes of the following detailed description, it is to beunderstood that the invention may assume various alternative variationsand step sequences, except where expressly specified to the contrary.Moreover, other than in any operating examples, or where otherwiseindicated, all numbers expressing, for example, quantities ofingredients used in the specification and claims are to be understood asbeing modified in all instances by the term “about”. Accordingly, unlessindicated to the contrary, the numerical parameters set forth in thefollowing specification and attached claims are approximations that mayvary depending upon the desired properties to be obtained by the presentinvention. At the very least, and not as an attempt to limit theapplication of the doctrine of equivalents to the scope of the claims,each numerical parameter should at least be construed in light of thenumber of reported significant digits and by applying ordinary roundingtechniques.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value, however, inherently contains certainerrors necessarily resulting from the standard variation found in theirrespective testing measurements.

Also, it should be understood that any numerical range recited herein isintended to include all sub-ranges subsumed therein. For example, arange of “1 to 10” is intended to include all sub-ranges between (andincluding) the recited minimum value of 1 and the recited maximum valueof 10, that is, having a minimum value equal to or greater than 1 and amaximum value of equal to or less than 10.

In this application, the use of the singular includes the plural andplural encompasses singular, unless specifically stated otherwise. Inaddition, in this application, the use of “or” means “and/or” unlessspecifically stated otherwise, even though “and/or” may be explicitlyused in certain instances. Further, in this application, the use of “a”or “an” means “at least one” unless specifically stated otherwise. Forexample, “an” aromatic monoacid, “a” polyacid, “a” polyol, “an”aliphatic polyacid, and the like refers to one or more of any of theseitems.

As used herein, the transitional term “comprising” (and other comparableterms, e.g., “containing,” and “including”) is “open-ended” and is usedin reference to compositions, methods, and respective component(s)thereof, that are essential to the invention, yet open to the inclusionof unspecified matter. The term “consisting essentially of” refers tothose component(s) required for a given embodiment and permits thepresence of component(s) that do not materially affect the properties orfunctional characteristic(s) of that embodiment. The term “consistingof” refers to compositions and methods that are exclusive of any othercomponent not recited in that description of the embodiment.

The coating composition prepared from an amine component of the presentinvention includes an amine component that comprises a polyaminecomplexed with CO₂ that is liquid at ambient conditions. As used herein,“ambient conditions” refers to room temperature and humidity conditionsor temperature and humidity conditions that are typically found in thearea in which the coating composition is being applied to a substrate.When reacted with a crosslinker, a liquid coating composition isprepared from the reaction mixture such that the entire system remainsliquid until curing. In one embodiment, the polyamine comprises ahindered polyamine which may be an aliphatic, cycloaliphatic, oraromatic polyamine. The amine component may include additional amines inaddition to the hindered polyamine, the additional amine being analiphatic, cycloaliphatic, and/or aromatic monoamine. To form a coatingcomposition, the crosslinker includes at least two functional groupsthat are reactive with the amines. Suitable functional groups includeisocyanate, oxirane, anhydride, aldehyde, ketone, beta-diketone,beta-ketoester, malonate, acrylate and/or fumarate components, and ofwhich may be aliphatic, cycloaliphatic, and/or aromatic. For example, inorder to produce polyurea, the crosslinker includes a multi-functionalisocyanate and which may further include a monofunctional isocyanate,oxirane, anhydride, aldehyde, ketone, beta-diketone, beta-ketoester,malonate, acrylate, and/or fumarate. It should be appreciated that thepresent invention describes certain embodiments where the amines used toproduce polyurea, however this is not mean to be limiting as the presentinvention may be used in other coating compositions that includereactive amines.

It is believed that the hindered amine is at least partially resistantto bonding with CO₂, so that the hindered amine complexed with CO₂ doesnot form a salt and remains liquid at ambient conditions, rendering theamine-CO₂ complex more readily handled than solid amine salt complex.The amine-CO₂ complex is liquid and stable at room temperature, so thatthe amine-CO₂ complex may be stored at ambient conditions for extendedtime periods. In addition, a reaction mixture including a crosslinkerand the amine-CO₂ complex of the present invention exhibits a longer potlife compared to a reaction mixture containing the same crosslinker andthe same amine that is not complexed with CO₂.

In use, the reaction mixture (polyamine complexed with CO₂ and acrosslinker) is handled so that the CO₂ dissociates from the polyamineat ambient conditions or elevated temperature such as up to 80° C. It isalso possible to include a catalyst or accelerant such as a mineral acidin order to accelerate rate of dissociation of the CO₂ polyamine. Forexample, the CO₂ may dissociate from the polyamine upon spraying oratomization of the coating composition at ambient conditions. Forexample, when a liquid reaction mixture comprising an amine componentcomprising a liquid polyamine complexed with CO₂ and a crosslinker(where the crosslinker includes functional groups that are reactive withamines) is sprayed onto a substrate such as a metallic or nonmetallicsubstrate, the CO₂ dissociates from the polyamine such that thepolyamine is reactive with the crosslinker and a coating compositionforms on the substrate.

It has been found that the CO₂-amine complex remains liquid at ambientconditions and can increase the pot life of a reaction mixture ascompared to a reaction mixture having the same amine that is notcomplexed with CO_(2.)

The following examples are presented to demonstrate the generalprinciples of the invention. The invention should not be considered aslimited to the specific examples presented. All parts and percentages inthe examples are by weight unless otherwise indicated.

EXAMPLES Example 1 Preparation of a CO₂-Amine Complex Resin

A CO₂-amine complex resin was prepared by adding 200.0 grams ofDESMOPHEN® NH 1420 to a 250 mL glass Erlenmeyer flask equipped with astirrer. CO₂ was then bubbled through the stirred amine resin at a rateof 1.0 standard cubic-foot per hour (SCFH) for five days at ambientconditions and under ambient atmosphere. The reaction mixture remained aclear and colorless liquid for the duration of the 5 day period, andthere was no apparent change in viscosity compared to the DESMOPHEN® NH1420 amine resin. The reaction mixture was then poured out into a glassjar and placed in an ambient temperature ultra-sonication bath for 30minutes (Fisher Scientific FS30H) to remove any excess CO₂ gas dissolvedin the reaction mixture.

Example 2 Coating Composition

A polyurea coating composition was prepared as follows using thecomponents of Table 1.

TABLE 1 2K Polyurea Pigmented Topcoat Preparation Coating ComponentsWeight A (Comparative) B (grams) DESMOPHEN ® NH CO₂-Amine Complex 27.61420¹ of Example 1 Eastman MAK² Eastman MAK 18.4 Acetone Acetone 11.6TINUVIN ® 292³ TINUVIN ® 292 1.1 TINUVIN ® 1130⁴ TINUVIN ® 1130 1.1DISPERBYK ® 2155⁵ DISPERBYK ® 2155 0.7 AEROSIL ® 200⁶ AEROSIL ® 200 0.2BYK-333⁷ BYK-333 0.2 MAPICO ® 1050A⁸ MAPICO ® 1050A 12.7 TIONA ® 595⁹TIONA ® 595 3.0 KROMA RED ® KROMA RED ® 0.1 RO3097¹⁰ RO3097 MONARCH ®1300¹¹ MONARCH ® 1300 0.1 CAT 143¹² CAT 143 23.2 ¹Amine-funcitonalresin, commercially available from Bayer Material Science. ²Methyln-amyl ketone, commercially available from Eastman Chemical Co. ³Lightstabilizer, commercially available from Ciba Specialty Chemicals. ⁴Lightstabilizer, commercially available from Ciba Specialty Chemicals.⁵Wetting and dispersing additive, commercially available from BYK⁶Hydrophobic fumed silica, commercially available from EvonikIndustries. ⁷Flow and leveling additive, commercially available from BYK⁸Ferric oxide hydrate (pigment), commercially available from Rockwood.⁹Titanium dioxide (pigment), commercially available from Crystal Global.¹⁰Ferric oxide (pigment), commercially available from Rockwood. ¹¹Blackpigment, commercially available from Cabot Corporation. ¹²PPG producedpolyisocyanate cross-linker

9.8 Grams of Eastman MAK, and all of the TINUVIN® 292, TINUVIN® 1130,DISPERBYK® 2155, MAPICO® 1050A, TIONA® 595, KROMA RED® R03097, andMONARCH® 1300 were added together in an appropriate sized container anddispersed under high shear force until a particle size of less than 10μm was obtained, determined by a Hegman “Fineness of Grind Gauge” inaccordance with ASTM D1210. For composition A, DESMOPHEN® NH 1420, theremaining solvents (8.6 g MAK and acetone), BYK-333, and AEROSIL® R-812were added and stirred under moderate to low shear conditions until theingredients were well incorporated and a homogeneous mixture wasobserved. For composition B, the CO₂-amine complex of Example 1 wasadded, the remaining solvents (8.6 g MAK and acetone), BYK-333, andAEROSIL® R-812 were added and stirred under moderate to low shearconditions until the ingredients were well incorporated and ahomogeneous mixture was observed. Composition B was then placed in anambient temperature ultra-sonication bath for 10 minutes to eliminateany remaining CO₂ gas from the liquid coating. A polyisocyanatecross-linker (HR-86-9357) was then added to both compositions A and B.The viscosity of both compositions A and B were measured just aftermixing with the cross-linker and periodically at 15 minute intervalsover the course of one hour using a Brookfield CAP 2000 high shearviscometer (#1 spindle, 75 RPM), as reported in Table 2.

TABLE 2 Viscosity Change of the Mixed Coatings Over One Hour Coating ATime (Comparative) Coating B (min) Visc (cP) Visc (cP) 0 20 25 15 60 4530 140 90 45 230 160 60 340 260

As can be seen in Table 2, the coating utilizing the CO₂-amine complexresin of Example 1 (Coating B) showed a lower viscosity at each 15minute interval compared to the Comparative Coating A utilizingDESMOPHEN® NH 1420 amine resin. Coating B exhibited a 23.5% lowerviscosity than Coating A after 60 minutes.

Immediately after mixing with the isocyanate cross-linker, Coatings Aand B were spray applied at ambient temperature and humidity conditionsusing a Graco AirPro compliant spray gun over an uncured solvent borne2K polyurethane primer on a Bondrite B-1000 iron-phosphate (withdeionized water rinse) treated cold-rolled steel substrate. The dry timeof the coatings at ambient temperature and humidity were measured bypressing on the coatings with a gloved finger (light applied force in 5minute intervals) until an indentation was no longer transferrable tothe coatings, at which point the coatings were deemed dry. After curingfor an additional 24 hours at ambient temperature and ambient humidity,both coatings were subjected to an MEK double rub test, in accordancewith ASTM D 5402, to determine the extent of curing. As reported inTable 3, the coatings showed equal dry times and similar cure responsesafter 24 hours.

TABLE 3 Comparison of Dry Times and Solvent Resistances of Cured FilmsCoating Dry Time MEK Double Rub Test A 40 min >100 double rubs(Comparative) B 40 min >100 double rubs

Although the present invention has been described with reference tospecific details of certain embodiments thereof, it is not intended thatsuch details should be regarded as limitations upon the scope of theinvention except insofar as they are included in the accompanyingclaims.

1. A liquid coating composition prepared from a reaction mixturecomprising (a) an amine component comprising a polyamine complexed withCO₂ and (b) a crosslinker, wherein said amine component is not a saltand is liquid at ambient conditions.
 2. The coating composition of claim1, wherein said polyamine comprises a hindered polyamine.
 3. The coatingcomposition of claim 2, wherein said hindered polyamine comprises analiphatic, cycloaliphatic, or aromatic polyamine.
 4. The coatingcomposition of claim 3, wherein said amine component further comprisesan aliphatic, cycloaliphatic, or aromatic monoamine.
 5. The coatingcomposition of claim 2, wherein said crosslinker comprises at least twofunctional groups reactive with amines.
 6. The coating composition ofclaim 5, wherein said functional groups comprise an isocyanate, oxirane,anhydride, aldehyde, ketone, beta-diketone, beta-ketoester, malonate,acrylate, and/or fumarate.
 7. The coating composition of claim 5,wherein said functional groups comprise an isocyanate, such that saidcoating composition comprises polyurea.
 8. The coating composition ofclaim 6, further comprising a monofunctional isocyanate, oxirane,anhydride, aldehyde, ketone, beta-diketone, beta-ketoester, malonate,acrylate, and/or fumarate.
 9. The coating composition of claim 6,wherein said crosslinker comprises an aliphatic, cycloaliphatic, and/oraromatic crosslinker.
 10. The coating composition of claim 1, whereinsaid CO₂ dissociates from said polyamine at ambient conditions.
 11. Thecoating composition of claim 1, wherein said CO₂ dissociates from saidpolyamine at an elevated temperature.
 12. The coating composition ofclaim 1, wherein said CO₂ dissociates from said polyamine with the aidof a catalyst or accelerant.
 13. The coating composition of claim 1,wherein said CO₂ disassociates from said polyamine upon spraying oratomization of the coating composition at ambient conditions. 14.(canceled)
 15. (canceled)
 16. A method of producing a coatingcomposition comprising applying onto a substrate a liquid reactionmixture comprising (a) an amine component comprising a polyaminecomplexed with CO₂ and (b) a crosslinker, wherein said amine componentis not a salt and is liquid at ambient conditions, whereby the polyaminedisassociates from the CO₂ and reacts with the crosslinker.
 17. Themethod of claim 16, wherein the reaction mixture is sprayed onto thesubstrate.
 18. The method of claim 17, wherein the substrate comprises ametallic or non-metallic substrate.
 19. A coated substrate comprising asubstrate and the coating composition of claim 1 applied to at least aportion of the substrate.
 20. The coated substrate of claim 18, whereinthe coating composition is sprayed onto the substrate.